While water treatment techniques are available to remove contaminants, e.g., metal contaminants and in particular, transuranic metal contaminants, it is desirable that such processes generate a minimum of resultant sludge or solid waste as increased cost for disposal of solid metal wastes has forced industries and governmental agencies to seek techniques that generate less solid waste in a cost effective manner. Presently, ferric or ferrous salts such as ferric sulfate, ferric chloride and ferrous chloride or ferrous sulfate are used as coagulants for removal of trace amounts of transuranic elements from wastewater streams. However, lower allowable standards for wastewater discharge may not be easily met by such coagulants without generation of excessive solid waste.
In the past few years, there has been increased interest by the water treatment industry in the use of ferrate salts as, e.g., a possible substitute for chlorination processes. For example, potassium ferrate may be used in the treatment and purification of water (see Murmann et al, "Experiments Utilizing FeO.sub.4.sup.-2 for Purifying Water". Water Research, Vol. 8, pp. 79-93 (1974); Gilbert et al, "An Investigation of the Applicability of Ferrate Ion for Disinfection", J. Am. Water Works, Vol. 68(9), pp. 495-497 (1986); and Waite et al., "Iron (VI) Ferrate as a General Oxidant for Water and Wastewater Treatment", Ozone/Chlorine Dioxide Oxid. Prod., Org. Matter Process Conference, (1976), published 1978, pp. 410-425). Ferrate salts are also known as useful for precipitation and/or coagulation of solids in the wastewater.
Stricter laws and regulations aimed at protecting public health and preventing contamination of the environment have been gradually instituted by various federal and state governmental bodies. For example, the Water Pollution Control Act and Safe Drinking Water Act have set specific requirements on the quality of water discharged into streams and served to the public as potable water. Other government agencies, such as the Department of Energy (DOE), have also promulgated orders setting permissible effluent discharge standards for transuranic elements and other radionuclides from DOE facilities. Presently, DOE Order 5480.1 derived concentration guideline sets discharge limits for plutonium 238, plutonium 239/240 and americium 241 at 1.times.10.sup.-4 microcuries per milliliter. A stricter standard is expected to issue by DOE in late 1989, setting limits for the plutonium and americium contaminants at 3-4.times.10.sup.-8 microcuries per milliliter. This standard may not be consistently achievable with the present processes of treating wastewater at DOE facilities.
Accordingly, it is one object of this invention to develop a process of treating transuranic element-containing water to reduce the level of transuranic element contaminants.
It is another object of this invention to remove transuranic elements from contaminated water to under anticipated governmental discharge limits, e.g., DOE effluent standards.
It is still a further object of this invention to minimize production of the resultant solid waste, i.e., sludge, upon removal of the transuranic elements from contaminated water.
Yet another object of this invention is to remove transuranic elements from contaminated water without increasing the levels of chemical additives presently used and without alteration of presently existing process equipment.